1. Technical Field
The present invention relates to a nitride based semiconductor device and a method for manufacturing the same, and more particularly, to a nitride based semiconductor device capable of having increased withstand voltage and being operated at low turn-on voltage to improve switching operating efficiency, and a method for manufacturing the same.
2. Description of the Related Art
Among semiconductor devices, there is a high electron mobility transistor (HEMT) using a two-dimensional electron gas (2DEG) as a current movement channel. A general high electron mobility transistor includes a base substrate such as a sapphire substrate, a nitride based epitaxial growth layer formed on the base substrate, and an electrode structure formed on the epitaxial growth layer. The electrode structure includes a gate electrode, a source electrode disposed at one side of the gate electrode, and a drain electrode disposed at the other side of the gate electrode. Generally, the gate electrode is a Schottky electrode forming a Schottky contact with the epitaxial growth layer, and the source and drain electrodes are ohmic electrodes forming an ohmic contact with the epitaxial growth layer.
In the nitride based semiconductor device having a structure as described above, current density and withstand voltage of the device should be increased in order to improve characteristics as a transistor and expand applications. However, there is a trade-off relation between the current density and the withstand voltage, such that when the current density is increased, the withstand voltage is decreased. For example, the current density is determined by ohmic contact resistance between the drain electrode and the source electrode and resistance of a channel, the withstand voltage is determined by withstand voltage between the Schottky electrode, which is the gate electrode, and the ohmic electrode, which is the drain electrode. Therefore, generally, the withstand voltage with respect to the ohmic electrode, which is the drain electrode, should be increased in order to increase the withstand voltage; however, in this case, a problem such as reduction in the current density, or the like, may be caused.